Caption: Atomic structure. Conceptual artwork depicting an atom (yellow ball) seen enlarged in a human hand. In the centre of the atom is the nucleus, made up of a tightly-packed cluster of protons and neutrons, around which electrons orbit. This classical atomic model is known as the Bohr Model, after the Danish physicist Neils Bohr. However, in modern quantum physics it has proved impossible to precisely locate the position of atomic electrons. Instead they are represented by fuzzy clouds, larger areas within which there is a high probability of an electron being found.